Until now, various techniques for music retrieval have been proposed for retrieving music that match with user preferences across a plurality of music. For example, Patent Literature 1 proposes a technique for music retrieval which utilizes feeling vectors representing a user's impression on music and the related feature vector representing the musical characteristics of that music. Patent Literature 2 proposes another technique for music retrieval using impression features that quantify user's impressions on music. Patent Literature 3 proposes a technique for music retrieval that employs preference information indicating a user's preference for any given music, feature quantities of that music, and how many times the music has been played.
Patent Literature 4 proposes a technique for music retrieval that employs music parameters that quantify features of music as one or more factors. Patent Literature 5 proposes a technique for music retrieval utilizing feature quantities of the frequency spectrum of music. Patent Literature 6 proposes a technique for music retrieval using numerical values that represent user's subjective requirements on music. Patent Literature 7 proposes a technique for music retrieval utilizing user profiles that represent musical preferences of a user.